Photodynamic therapy (PDT) is commonly administered to a treatment site that is disposed on or within a patient's body using a light source that is energized with an electrical current. The light source, which may be positioned either external or internal to the patient's body, emits light having a characteristic wave band selected to match an absorption wave band of a photodynamic reagent that has been administered to the treatment site. The photoreactive reagent is preferentially absorbed by abnormal tissue at the treatment site. When exposed to the light, the abnormal tissue that has absorbed the photoreactive agent is destroyed.
U.S. Pat. No. 5,445,608 (Chen et al.) discloses that even relatively low intensity light, such as that produced by light emitting diodes (LEDs), can be very effective in destroying abnormal tissue and undesired organisms within a patient's body. Because of the relatively low intensity of the light emitted by an LED compared to a high power laser, the treatment is preferably administered for an extended period of time, or at least for a longer time than would be done if a high intensity laser light source were used as the light source. This patent reference also discloses several embodiments for probes that includes such low intensity light sources and which are intended to be implanted within a patient's body to administer PDT for relatively longer periods of time, thereby destroying a tumor or abnormal cells at an internal treatment site. However, electrical power must be supplied to energize the light sources on the implanted probe. The patent teaches that either a battery and/or an internal power supply receiving energy from an external power source, e.g., by electromagnetically coupling the internal power supply to the external power source, can be used for energizing the light sources on the probe.
Clearly, there would be significant advantages in developing a system for delivering light therapy that does not include a battery, does not require recharging, and which does not require any energy transfer from outside the patient's body. Instead, such a system would be self-powered to obviate the need for continual or intermittent power transfer from an external power source. By eliminating a battery supply and/or a power receiver coil, a system for administering PDT could be substantially simplified, requiring fewer components, and could be greatly reduced in size. This reduction in size might facilitate the administration of PDT to an internal treatment site not readily achieved with larger and more complex devices that must be intermittently coupled to an external power source or which must include a relatively large power storage device.
It would also be desirable to enable a light source disposed within a patient's body to be easily moved to a treatment site and maintained at that position. Further, once the light therapy has been completed, it would be desirable to enable the light source to be readily removed from the patient's body, preferably without the need for invasive surgery. The self-energized light source should also preferably be sealed to minimize any risk of exposure of the patient to components of the system used to administer the therapy that might be toxic and to protect the light delivery system from damage due to exposure to bodily fluids.